1. Field of the Invention
This invention relates to an apparatus of a multiple-stage grinding machine for grinding and removing burrs in a continuous rolling process where billets are joined together by a flash butt welding method.
2. Description of the Related Art
In the continuous rolling process, the successively casting billets are joined together at the inlet of a rolling mill, making use of the flash butt welding method. And then, a contiuous billet can be formed. Finally, the continuous rolling process, what we call, Endless Rolling Process, can be obtained. However, the said process has a possibility to bring about an uplifted welded part with spills (which are caused by an untrimmed laminated part line) and other defects. As a result, the as-welded billet has been rolled without any corrective action. No satisfactory product can be produced in such a way, from a view point of the product quality. Consequently, the burr on the welded part is in need of being removed before being processed by the rolling mill.
In case of a square billet, a burr-removal apparatus has been disclosed in `unexamined Japanese patent publication No. 52-43754, examined Japanese patent publication No. 57-11722. ` Such a disclosed burr-removal apparatus utilizes formed turning tools or those which face each other against its opposite side, in order to remove the said burr on the welded part. This apparatus has, however, disadvantages of suffering severe abrasion on the turning tool and of spending a lot of time on exchanging the turning tools. By that reason, this apparatus is not suitable for being applied to the continuous rolling process under the usual operating condition of 24 hours continuously.
Furthermore, a method has been known to grind burrs on the welded part by a grinding machine, syncronizing the grinding machine with the travelling billet. (See unexamined Japanese patent publication No. 9-66450, unexamined Japanese patent publication No. 9-122918). However, such a method requires that the grinding machine travel, simultaneously with the travelled billet itself, for a required time (3-10 sec. ) to be grinded. This causes some problems with respect to space-arrangement and the instrumentation control system.
But, in such a continuous rolling process for billets, the grinding method is the most suitable for removing burrs on the welded part because it meets severe operative rolling conditions. In such a case, under the condition of using the travelling grinding machine, the large space for travelling is required. In addition, a complex instrumentation control system is required for synchronizing the grinding machine with travelling speed of billet. On the other hand, the fixed grinding machine does not require a large space nor a complicated control system, but taking its grinding capacity into consideration, a single-stage grinding method cannot deal with the whole of the successively occurring welded parts.